Stimulation of G-protein coupled receptors in vascular smooth muscle cells induces tyrosine kinase dependent increases in calcium without tyrosine phosphorylation of phospholipase C gamma-1.
It is often believed that increases in intracellular Ca2+ ([Ca2+]i) resulting from stimulation of G-protein coupled receptors in vascular smooth muscle cells (VSMC) require activation of the beta1 isoform of phospholipase C (PLC). However, recent studies showed that rat aortic VSMC do not express PLC beta-1 and that stimulation with angiotensin-II induces tyrosine kinase dependent increases in [Ca2+]i and tyrosine phosphorylation of PLC gamma-1. Whether this pathway is activated by other vasoactive agents that stimulate G-protein coupled receptors is unknown. Here, we show that A10 VSMC express PLC beta-2, PLC beta-3, PLC delta-1, and PLC gamma-1. The cells also expressed Galpha(q/11). However, neither PLC beta-1 nor PLC beta-4 was detected. Stimulation with angiotensin-II, vasopressin, serotonin, or endothelin induced tyrosine kinase dependent increases in [Ca2+]i. However, tyrosine phosphorylation of PLC gamma-1 did not occur. In contrast, stimulation with platelet derived growth factor increased [Ca2+]i and tyrosine phosphorylation of PLC gamma-1. The results show that tyrosine phosphorylation of PLC gamma-1 is not required for tyrosine kinase dependent increases in [Ca2+]i resulting from stimulation of diverse G-protein coupled receptors in VSMC.
Di Salvo
J
J
Department of Physiology, University of Minnesota, Minneapolis 55455, USA. disa1001@gold.tc.umn.edu
Raatz Nelson
S
S
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D002460:Cell Line; D016232:Endothelins / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D019833:Genistein / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D051966:Phospholipase C gamma; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000032:analysis / Q000276:immunology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism*; D014667:Vasopressins / Q000494:pharmacology
D016232:Endothelins; D007527:Isoenzymes; D010982:Platelet-Derived Growth Factor; D011956:Receptors, Cell Surface; D014667:Vasopressins; D000804:Angiotensin II; D019000:Phosphotyrosine; D012701:Serotonin; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D019204:GTP-Binding Proteins; D002118:Calcium